This invention relates in general to improved methods for producing standard PCMCIA electronic packages (i.e., PC cards) or small form factor electronic packages and the cards produced thereby.
The Personal Computer Memory Card International Association (PCMCIA) is a standards body composed of more than 300 member companies. PCMCIA has developed standard sized electronic packages for personal computers cards (i.e., PC cards). A PC card is standardized in size for use in personal computers, personal communicators, and other electronic devices. PC cards are used to provide additional memory, storage, communication and input/output (I/O) capabilities, especially for portable systems.
PCMCIA standards describe the physical requirements, electrical specifications and software architecture for PC cards. The standards define three physical sized cards: Type I, Type II and Type III. The thickness is the only difference between the three types. The thicknesses for Type I, Type II and Type III are 3.3, 5.0 and 10.5 millimeters, respectively. All three types use a standard 68 position connector for connecting to the computer or other device.
There are various methods of producing each of the different sizes of PC cards. Each method consists essentially of producing a printed circuit board or substrate with electronic components thereon. Attaching a frame around the printed circuit board and applying covers (or lids) on either side of the printed circuit board. If the PC card uses the single 68 position connector, the printed circuit board simply slips into the frame, and the connector locks in place. If the PC card also has a "back end" connector. Typically, the "back end" connector is attached to the frame and then attached to the printed circuit board using a soldering process.
A ground clip is typically attached either to the side of the frame to ground the PC card to the computer's internal ground or is attached to the printed circuit board. Two metallized covers are attached to the printed circuit board-frame assembly (one on each side) to protect the electronic components therein.
The most common cover type is the adhesive-backed metal lid. A press applies both heat and pressure to attach the cover to the frame. The covers must be hand-aligned on the assembly and placed into the press at about 120.degree. C. for 20 seconds under pressure. The unit is then allowed to cool in the press to prevent cold flow or lifting of the cover from the frame. The total process time for this assembly is typically 180 seconds. Typically, springs are placed between the lids and the printed circuit board to prevent electromagnetic interference (EMI) problems.
Another type of lid is the staple lid, which is a cover with metal tabs for protruding through the frame. The tabs are typically crimped around the frame. Assembly is simple but requires a die and press. The two covers are hand-aligned on the frame. The assembly is the placed into the press, pressure applied and the crimps made. The attachment process is around 60 seconds but the tooling cost is higher than the adhesive-backed metal lids because of the cost of the die set.
Another type of cover is the injection-molded frame/cover combination. This method involves injection-molding a frame around the edges of a top cover and injection-molding a frame around the edges of a bottom cover, thus eliminating the frame as a component separate from each of the covers. The two frame/cover assemblies are placed on opposite sides of the printed circuit board and ultrasonically welded together. Process time is around 30 seconds but the ultrasonic welding step is costly.
The final type is a "snap together" configuration. The covers are simply snapped together over the rails of the frame around the printed circuit board. Ground tabs are incorporated into the covers that are bent in such a manner as to contact pads on the printed circuit board without the need for soldering. The process time is around 20 seconds.
U.S. Pat. Nos. 5,173,840 and 5,244,840 issued to Kodai et al. disclose using a molded frame and placing a printed circuit board with electronic components thereon into the frame, then filling the space defined by the frame with resin to cover the surface of the printed circuit board.
There is a continuing need in the art for a high strength, cost-effective method for producing standard electronic packages meeting the requirements of the PCMCIA standards.